In the never ending quest for faster computers, engineers are linking hundreds, and even thousands of low cost microprocessors together in parallel to create super supercomputers that divide in order to conquer complex problems that stump today's machines. Such machines are called massively parallel. We have created a new way to create massively parallel systems. The many improvements which we have made should be considered against the background of many works of others.
Multiple computers operating in parallel have existed for decades. Early parallel machines included the ILLIAC which was started in the 1960s. ILLIAC IV was built in the 1970s. Other multiple processors include (see a partial summary in U.S. Pat. No. 4,975,834 issued Dec. 4, 1990 to Xu et al) the Cedar, Sigma-1, the Butterfly and the Monarch, the Intel ipsc, The Connection Machines, the Caltech COSMIC, the N Cube, IBM's RP3, IBM's GF11, the NYU Ultra Computer, the Intel Delta and Touchstone.
Large multiple processors beginning with ILLIAC have been considered supercomputers. Supercomputers with greatest commercial success have been based upon multiple vector processors, represented by the Cray Research Y-MP systems, the IBM 3090, and other manufacturer's machines including those of Amdahl, Hitachi, Fujitsu, and NEC.
Massively Parallel Processors (MPPs) are now thought of as capable of becoming supercomputers. These computer systems aggregate a large number of microprocessors with an interconnection network and program them to operate in parallel. There have been two modes of operation of these computers. Some of these machines have been MIMD mode machines. Some of these machines have been SIMD mode machines. Perhaps the most commercially acclaimed of these machines has been the Connection Machines series 1 and 2 of Thinking Machines, Inc.. These have been essentially SIMD machines. Many of the massively parallel machines have used microprocessors interconnected in parallel to obtain their concurrency or parallel operations capability. Intel microprocessors like i860 have been used by Intel and others. N Cube has made such machines with Intel '386 microprocessors. Other machines have been built with what is called the "transputer" chip. Inmos Transputer IMS T800 is an example. The Inmos Transputer T800 is a 32 bit device with an integral high speed floating point processor.
As an example of the kind of systems that are built, several Inmos Transputer T800 chips each would have 32 communication link inputs and 32 link outputs. Each chip would have a single processor, a small amount of memory, and communication links to the local memory and to an external interface. In addition, in order to build up the system communication link adaptors like IMS C011 and C012 would be connected. In addition switches, like a IMS C004 would provide, say, a crossbar switch between the 32 link inputs and 32 link outputs to provide point-to-point connection between additional transputer chips. In addition, there will be special circuitry and interface chips for transputers adapting them to be used for a special purpose tailored to the requirements of a specific device, a graphics or disk controller. The Inmos IMS M212 is a 16 bit processor, with on chip memory and communication links. It contains hardware and logic to control disk drives and can be used as a programmable disk controller or as a general purpose interface. In order to use the concurrency (parallel operations) Inmos developed a special language, Occam, for the transputer. Programmers have to describe the network of transputers directly in an Occam program.
Some of these massively parallel machines use parallel processor arrays of processor chips which are interconnected with different topologies. The transputer provides a crossbar network with the addition of IMS C004 chips. Some other systems use a hypercube connection. Others use a bus or mesh to connect the microprocessors and there associated circuitry. Some have been interconnected by circuit switch processors that use switches as processor addressable networks. Generally, as with the 14 RISC/6000s which were interconnected last fall at Lawrence Livermore by wiring the machines together, the processor addressable networks have been considered as coarse-grained multiprocessors.
Some very large machines are being built by Intel and nCube and others to attack what are called "grand challenges" in data processing. However, these computers are very expensive. Recent projected costs are in the order of $30,000,000.00 to $75,000,000.00 (Tera Computer) for computers whose development has been funded by the U.S. Government to attack the "grand challenges". These "grand challenges" would include such problems as climate modeling, fluid turbulence, pollution dispersion, mapping of the human genome and ocean circulation, quantum chromodynamics, semiconductor and supercomputer modeling, combustion systems, vision and cognition.
As a footnote to our background, we should recognize one of the early massively parallel machines developed by IBM. In our description we have chosen to use the term processor memory element rather than "transputer" to describe one of the eight or more memory units with processor and I/O capabilities which make up the array of PMEs in a chip, or node. The referenced prior art "transputer" has on a chip one processor, a Fortran coprocessor, and a small memory, with an I/O interface. Our processor memory element could apply to a transputer and to the PME of the RP3 generally. However, as will be recognized, our little chip is significantly different in many respects. Our little chip has many features described later. However, we do recognize that the term PME was first coined for another, now more typical, PME which formed the basis for the massively parallel machine known as the RP3. The IBM Research Parallel Processing Prototype (RP3) was an experimental parallel processor based on a Multiple Instruction Multiple Data (MIMD) architecture. RP3 was designed and built at IBM T. J. Watson Research Center in cooperation with the New York University Ultracomputer project. This work was sponsored in part by Defense Advanced Research Project Agency. RP3 was comprised of 64 Processor-Memory Elements (PMEs) interconnected by a high speed omega network. Each PME contained a 32-bit IBM "PC scientific" microprocessor, 32-kB cache, a 4-MB segment of the system memory, and an I/O port. The PME I/O port hardware and software supported initialization, status acquisition, as well as memory and processor communication through shared I/O support Processors (ISPs). Each ISP supports eight processor-memory elements through the Extended I/O adapters (ETIOs), independent of the system network. Each ISP interfaced to the IBM S/370 channel and the IBM Token-Ring network as well as providing operator monitor service. Each extended I/O adapter attached as a device to a PME ROMP Storage Channel (RSC) and provided programmable PME control/status signal I/O via the ETIO channel. The ETIO channel is the 32-bit bus which interconnected the ISP to the eight adapters. The ETIO channel relied on a custom interface protocol with was supported by hardware on the ETIO adapter and software on the ISP.